1. Field of the Invention
The invention concerns a high frequency radiation cable, and more particularly, a high frequency radiation cable with groups of periodically arranged openings in the outside of the conductor cable.
2. Description of the Prior Art
A radiation cable or a leakage cable is a waveguide made from a coaxial cable, which has openings in periodic sequence on the outside conductor. Electromagnetic fields pass through these openings into the outer cable space. The output to be radiated is supplied at one end of the cable. Because of natural cable attenuation, the intensity of the radiated output decreases along the length of the cable. In practice, this means that the sum of line and coupling attenuation between a vehicle and the radiating wave guide increases with the distance of the vehicle from the high frequency supply point. It would therefore be desirable to vary the energy coupling along the wave guide or the cable, so that the received field strength is kept constant in the mobile component.
A leakage cable is known from European patent application EP 188 347, wherein the outside conductor of the coaxial cable consists of bands surrounding the central conductor in a helix, and which overlap so as to form diamond-shaped gaps. These gaps get larger at the end of the cable, i.e. with increasing distance from the supply point, so that more energy can be radiated.
The disadvantage of this process, in addition to the high cost, is that enlarging the openings or holes only produces a relatively small increase in radiation.